Description:

The impact of global climate change factors such as increased temperature and ultraviolet radiation (UVR) on coral bleaching are of continued interest to the USEPA. Coral bleaching occurs when symbiotic zooxanthellae and/or their pigments are depleted in response to stressors such as temperature and salinity extremes, disease, and UVR exposure. The bleaching response to enhanced UVR was studied in corals from Hawaii and the Caribbean by exposing whole corals to UVR in a solar simulator. When visible bleaching was observed (4-5 days), experiments were terminated, coral tissues were harvested, and measures of zooxanthellae number, photosynthetic pigment content and tissue protein were employed. Zooxanthellae number was the most sensitive measure that correlated with bleaching in some coral species. Reduced zooxanthellae per polyp were found in Caribbean corals exposed to the highest UVR treatment compared to UVR-free controls; while UVR-exposed Hawaiian corals had either increased or unchanged average zooxanthellae densities. No trends emerged in pigments normalized to polyp or zooxanthellae number, nor in tissue protein content among the 5 species of corals tested. These results may be due to the short exposure duration, high within-treatment variability, and/or the tissue harvesting method utilized. Modifications to the solar simulator are under way to allow longer-term exposure of corals under culture-like conditions. Future experiments will employ corals successfully maintained in long-term culture, increased replication within treatment, gradual acclimation of corals to test conditions, and dual exposure to variable UVR levels and temperatures.

Purpose/Objective:

Modifications to the solar simulator are under way to allow longer-term exposure of corals under culture-like conditions

Record Details:

Record Type: DOCUMENT (PRESENTATION/ABSTRACT)

Start Date: 07/01/2003

Completion Date: 07/01/2003

Record Last Revised: 10/02/2012

Record Created: 09/26/2003

Record Released: 09/26/2003

OMB Category: Other

Record ID: 62611

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB
GULF ECOLOGY DIVISION
BIOLOGICAL EFFECTS AND POPULATION RESPONSE BRANCH